Process for obtaining butadiene in a more concentrated form



and pertains particularly to such operations synthetically. a epyrolysis of petroleum or spection of the specification and claims;

form from mixturesof butadiene by; the-iforma" division is described andclaimed. Exceptionally suita le t p rature and p ssure condit -30articles having a diameter or, less than'0.05 mm,-

sfterward dissociated, f v after Separation betterre sults are obtainedwhen at least the from the unreacted material, to liberate the butamajorportion of dry reagent n; comprises diene a regenerate the reagent salt.u particles having a diameter of less than 0.02 mml, sociation ordecomposition may be carriedout by 35 and particularly l tha l 0.01 mm.

" inclfease in t and/ c n? I have discovered that butadienefmay be obinpressure- "tained more readily and/or in a higher stateof low cost, andavailability; Cuprous chloride is 9. 113 and 11B of the periodic systemwhen such op .Pfi y v desirable lt to be used for this erations areconducted at leastein part under subpurpose.

' highly concentrated, or substantially pure form,

Patented Mar. V I I p n v UNITED STATES PATENT l o -lc;1-: A 1 e. v. v2,395,959 I v i PROCESS ronon'mmmo BUTADIENE m A i r ona CQNQENTRATEDFORM, "Freer J. Soday,Swart hmore, ragss lzno to The 7 United GasImprovement Com'panmacorpora- F10 M'l'elmsylvanla c No Drawing.Application October 30,1942, i Serial No. 463,947 l V 8Claim s;(clzeo-eslsy p v p 7 p This invention relates to=the concentration of -lfra ybe employed for this D dioleflnes, I -V po l r 1 v. 1 Moreparticulafly, this inyentibn rt 'I'he butadiene 1 fractions and/ormixtures erallyto the recovery 'ot'buta'dienein more con-r which may becomentrawd by my Process centrat form from liquids containing t same, be7 obtained from any desired source, such as wherein solid dry salts ofmetals of groups IB and petroleum hydrocarbons by thePyrolysis 11 of tperiodic system ar empyed v dehydrogenation of organic materials in gennj Of the Present invention is the prosuch as almhol- I a v I duction ofrelatively large proportions of concen- 0 described a claimed in mimpending zrated butadiene from a more dilute fraction or plication i451187; filed September mixture containing the same. Another object of w1942' the emclency '1 solid dry reagent the invention is the productionofa by-product salts 15 increased suPstanm-iny by the incorpom' fractionor mixture containing relatively. small, therein i a 5 immmq h substanceor negligible, proportions of butadine. Other 15 Such as an alkali metaland/m7 an objects and advantages or the -invention will be Xideofanv-alkalme earfih F inwnilmctim apparent tolthose skilled m the artupon an with a polymerization inhibitor, such'ras a sec ondary'arylamine; a polynuclear phenol, a polyhydroxy-phenol, and/or a substitutedphenolic material; and the reactionproduct ofvan aldee hyd'e or a ketonewith an amine. l p In my copending application, Serial No. 460,692,

- Soliddry salts of metals of groups'IBand IIB of the periodic systemand particularly mono valent saltstof heavy metals of thesegroups, suchas the halides, nitrates, sulfates, phosphates, formates,acetates,lactates, propionates, and car- 2 23 g g g fig g gfigg g zgaggggzgg fi' bont ,1 f emsshisitizzsssszrn 25 mm by of a sat type describedin an unusually fine state of subtion of an association product, or acomplex, of desirable results t r v V V s obtained when at least the,butadiene with one or more of said salts under I major portion of the myreagent salt comprises which complex or association product may be 7and, more particularly, less than 0.03 mm. Even Monovalent cuproussalts" are verydesirable purity from dilute fractions and/or mixturesconagents f u e in concentrating Processes of this taining the same inprocesses involving the use of type due to their stability, ease of regnerat on; 40 at least one solid, dry salt or a metal ofgroups l ratmospheric pressures and temperatures of not- F q y, it is found to betechnically adv nless than 25 C., and more particularly not lesstageousto first resort to fractionaldistillation '45 th 30 c, 3 V v vother means r o the boiling ran f t The concentration of butadiene bythe applibutadiene fraction or mixture. Thus, a l-C4 cut cation 01' oneor more reagent salts of theotype' containing b tadiene, b n s. n p rhps, described customarily is conducted by contacting butanesmaybetreated to obtain a more highly the butadiene fraction or mixturewith.the deconcentrated butadiene fraction. v 0 sired reagent salt underconditions designed to Such concentrated butadiene'fractions may be forma complex or addition-product betweenthe treated wi solid d re s gs' 0fh ype butadiene and the reagent salt; permitting the described herein toisolate the butadiene in more reaction to proceed to the desired extent,removl l ing the unreacted portion of the said fraction or or widerboiling fractions and/orjless concenmixture sllch as bydistillatlon, anddecomposing the addition product by the application of elevatedtemperatures to regenerate the butadiene in more concentrated, orsubstantially pure, form.

This operation is somewhat time consuming, particularly when a producthaving a fairly high degree of purity, such as a, product having aconcentration of butadiene of not less than 90%, and

more particularly, not less than 95%, is desired.

In addition, the product obtained frequently contains less than thedesired concentration of butadiene and/or the initial by-productfraction secured contains more than the permitted proportion ofbutadiene. If an intermediate fraction, which may be referred to astherecycle fraction, is taken, this also may contain an unduly largeproportion of butadiene.

These undesirable results appear to be due, at

tion of the butadiene in 'the initial by-product,

fraction and/or in the intermed ate or recycle fraction, if anyintermediate fraction is collected; and/or the isolation of a productcontaining less than the desired proportion of butadiene.

The foregoing may be summedup by stating that the retention of unreactedmaterial by the reaction mass frequently leads to the production of abutadiene concentrate containing less than the desired proport on ofbutadiene and/or to the isolation of unduly large proportions ofbutadiene in the initial and/or intermediate fractions.

The concentrating process may be considered to consist of the followingseries of operations.

. reagent salt complex in order to prevent the decomposition of anunduly large proportion of this material, during the removal of theunreacted material. When cuprous chloride is employed as the reagentsalt, the complex formed between this material and butadiene has a vaporpressure 01' 760 mm. at a temperature of approximately proximately 250mm., and at C. a vapor pressure of '70 mm. a

The preferred upper'temperature limit to be employed in the removal ofthe unreacted material depends largely upon the pressures under whichsuch operations are conducted. In gen- 2 $0 chloride, the oleflnspreferablyare-removed at a temperature'not exceeding 59 C. at 760 mm.,45 C. at 250 mm., and 30 C. at '70 mm.

It should be understood, of course,.that somewhat higher temperatures,which may approach 85 or equal that of the decomposition point of thebutadiene-reagent salt complex, may be employed for a relativelyshort-portion of time near the end of this operation if a product havingan unusually high degree of purityis required. Even 40 in such cases,however, I generally prefer not to 1. Absorption of the butadiene fromthe fraction or mixture by the reagent salt,"resulting in the formationof an addition compound between the b tadiene and the reagent salt.

2. The removal of the unreacted material, usually by distillation, whichmay be carried out ,in such a manner as to form one or more cuts.

When multiple cuts are taken, the finalcut, or any mixture of cuts otherthan the initial cut, may be designated as the recycle stock.

3. The desorption of the addition compound, usually by the applicationof heat, to liberate the butadiene, and regenerate the reagent salt.

As pointed out previously, I have discovered that such operations may becarried out in a more satisfactory manner by the application of reducedpressures in coniunction with the use of a temperature of not less than25 C. during at least a portion of the said operations. 7

The benefits of this invention may be substantially realized by removingat least the latter portions of the unreacted material under reducedpressures and the application of temperatures of not less than 25 C.Thus in the concentration of a butadienefraction, after the absorptionhas been completed a portion of the unreacted material may be removed byreleasing the pressure on the system and/or by the application of heat,care being taken not to exceed the decomposition point of thebutadiene-reagent salt complex. The pressure on the system then isreduced until employ temperatures of that order, but rather tocontinue-the removal of unreacted material at temperature within thelimits set forth previously for a somewhatlonger period of time. 7

After removal of unreacted material, the reagent s'alt-butadiene complexmay be decomposed by heating it to a temperature equal to or greaterthan that required to decompose it at the pressures employed, and/or bya further reduction in pressure to accomplish the same purpose. Thedesorption operation may be carried out under subatmospheric,atmospheric, or superatmospheric pressures.

The concentration of a butadiene fraction or mixture by this. method maybe summarized briefly as follows. The absorption may be carried out atany desired pressure, although atmospheric or superatmospheric pressuresare preferred. The absorption temperature may be varied somewhat, but Igenerally prefer to employ temperatures not exceeding40 C., and moreparticularly temperatures not exceeding 30 C., at atmospheric orsuperatmospheric pressures. The removal of unreacted material is carriedout by the application, for at least, a portion of the time, ofsubatmospheric pressures and temperatures of not less than 25 C. Themaximum temperature employed at this stage of the operation preferablyis at least 5 C. below the decomposition point of the butadiene-reagentsalt complex. The desorption operation, in which the butadiene isrecovered in more highly concentrated and/or purified form may becarried out at subatmospheric, atmospheric, or superatmosphericpressures, preferably employing a temperature equal to or greaterthanthe decomposition point of complex at the presthe butadiene-reagentsaltsure employed. 7 r v I By the use of temperatures of at least Ci. andmore preferablyat least C. under sub;

havingone dimension at least twicethe magni-v tudeof the otherdimension, and preferably even -i-.ni ore,,such-as rods or rodrshap dobjects. The

atmospheric pressures for the removal of at least a portion of theunreacted material present, an I olefine fraction containing lessbutadiene and a butadiene concentrate containing higherv percentagesofrbutadienaas well'as higher yields of such butadiene concentrate, isobtained than when lower temperatures, such as 20 C. or lower, areemployed for the same period of time.

The concentrating process may be carried out- A' satisfactory method.

in any desired manner. involves the use of a ball, rod, "or other millcapable ofmaintaining the reagent salt in the Themill or vessel atleast: equal in weight to-the weight of thereagent .salt, and morepreferably at least three times the weight of the reagent salt.

When chains are employed such units may be used alone or'in combinationwith other -:units such as balls, rods, or other grinding, or crushing.

devices. The chains may be employed loosely in the mill or they may beattached to the walls or sides thereof at one or' more points. In casethe chainsaw attached to the inner surface of the unit, a curtain eflectis achieved which, greatly assists in breaking unthereagant mass and intransmitting heat therethrough. I T

'In this connection, it is well to optimum results are. achieved whenthe reagent salt is maintained ,in a state of very fine subdivisionduring the absorption desorption cycle and or pebbles are employed forthis purpose, the quantity used preferablyshould be point out that.

rods'may be of any-desiredlength, and may'con I tainany number and typeof projections along their long axis to serve as abraders to keep theinner surface ofthe mill clean.

It -is to be understood, of course, that more than one type ofirregularly shaped object may be employed simultaneously in the mill,and that such irregularly shaped objects may be used in conjunction withthe usual type of spherical ob- Jects, such as metallic balls orfiint,pebbles.

Another satisfactory. method for maintaining the reagent salt injthedesired state of very fine subdivisionis the use of ascraping agitatoror a plow on the inner wall of the mill. The scraping agitator maycomprise a blade extending the entire length vof the mill and .mountedona support by means of freelyswinging pivots. By the use .0: suitablesprings, the scraping blade may be urged (against theinnerwall of themill with,

I sufllcient force to effectively remove any deposits of dry reagentsalt: thereon. Such scraper blade preferablyiis used in conjunction withspherical.

or non-spherical metallic, or other, objects which serve to maintain theloosened mass in the"-deveryflne state of subdivision. In order nottointerfere with the action of the balls or other the surfacev of themill or other reaction unit is relatively, free of reagent salt and/orother deposits. sum deposits interfere with heat-exchange relationshipsand tend to retard the volatilizationfof any unreacted and/or liberatedhydrocarbon materials present in the deposit. 7 V

In my copendlng application. previously re ferred to,,specific methodsfor accomplishing theseresults are described and claimed. These; includethe. use .of a wall-scrapingunit, a plo or similar cutting device; theuse of irregularlyshaped'grinding objectsjand/or the use of special ballor other grinding or milling units, such as a double-conical ball mill.

Thus, the dry reagent salt may be reduced to, and maintained in, thedesired degree'iof subdivision bythe use of irregularly shaped abradingobjects, either alone orin conJunction with thespherical objectsnormally employed for this purpose in typical ballmill operations. j

"Such irregularly shaped objects are designed to scrape, rather thanroll, over the innersurface of the mill, thuskeeping it clean andpreventing the formation of a layer of reagent salt thereon.

With the walls of the millclean at all times, thus eliminating anycushioning effect during the grinding operations, the formation ofagglomerized particles in ,the interior of the reaction mass a, also islargely. if not entirely. prevented.

These irregularly shq ed objects mayha've alabrading devices, thescraper blade should be placed outside the zone of operation of such'ob-'jects. 'As this includes the bottom of the mill and at least. a portionof the side toward which the millis rotating the scraper blade, orblades, should be placednear, or at, the top of the mill,

or at the opposite side of the mill, that is, at the clean side of themill. The use of more than one scraper blade will be found to bedesirable in certain instances, and at least one of'the bladesmay beprovided with a serrated edge, or with teeth or other cutting units; toassist'in' breaking'up the. deposit of dry reagent salt on the innersurface of the mill.

, An alternative method of operating the mill comprises maintaining themill in a stationary position, and" rotating "the scraper blade, orscraper blades, therein. In this method of operation, the scraper bladespreferably are attached to a fairlybroad 'support, or blade, whichserves to revolve the balls, or other objects, contained in the mill toassist in pulverizing the rea entmass- In place of the scraper blade, orblades, a plow arrangement may be employed to remove any deposits fromthe'inner surface of themill. This plow which may be of anysuitabledesign and may possess a straight or'serrated cutting edge, or beprovided with teeth, prongs, or other cutting or digging devices, issuitably arranged to operate in a slot, depression, or track in asupporting member extendinglengthwise of the mill, andissuitablyurgedagainst; the inner surface of the millto remove deposits ofreagentsalt formed thereon by means of a spring, or springs,

most anyv desired form,such as loblong, pyramidal, hexagonal,octagonal,cylindrical, and the like. Particularly desirable; types are objectswhich may be of the coil, leaf, or otherdesired type. The movement ofthe'plow back, and forth along the "long axis of the mill, together withthe circularmotion of the 'mill, serves to effectively remove anydeposits of reagent salts on the inner surface of. the mills. I

; As in the case of the scraper previously describedftheplow preferablyis employed in conjunction with grinding or pulverizing agents,

such as spherical balls'an'd/or irregularly shaped metallic, or otherobjectswhich serveto maintain the reagent salt in a very fine state ofsubdivision. In such case, the plow and its supporting member preferablyis located in such position as not to interfere with the grinding andpulverizing action of the balls, or other objects,

present.

A plurality of plows also may be employed, and such units may be aflixedto one, or more than one, supporting member.

As in the case of the-scraping agitator described previously, the plowand its supporting member may be revolved in a stationary mill, in whichcase the supporting member or supporting members preferably are of suchdesign as to impart suiiicient motion to the balls, or

other pulverizing agents, present in the mill to' maintain the reagentsalt in the desired very finely divided state.

Very satisfactory results also may be obtained by the use of a doubleconical mill. In this type of mill, the design is such as to impart botha. sliding and rolling motion to'the balls or other pulverizing agentsemployed therein, and to increase the efiective pulverizing action ofthe said balls by causing the material to pour in the rolling streaminto the lower cone at each half revolution, striking the wall of thatcone, and curling upward and over toward the center, each particletaking a different course because. of the cone surface. The apices ofthe truncated cones are perpendicular to the axis of rotation. Thisincreases the efiective velocity of the'balls, and hence their grindingand pulverizing action. The use of non-spherical objects, either aloneor in conjunction with spherical balls and/or pebbles,

and/or possibly the use of scraping agitator and/or a plow, in a doubleconical mill will be found to giveexcellent results.

It is to be understood that any of the foregoing methods for reducing,and maintaining, the reagent salt in the desired very finely dividedstate may be used alone, or in any desired combination. I

The process is more particularly illustrated by means of the followingexample.

Example 1 A 50% butadiene fraction was contacted with an excess offinely divided cuprous chloride in a horizontal ball mill for a period.of 110 minutes at a temperature of 25 C. and a pressure of 40 lbs/sq.in. A portion of the'unreacted material was removed by reducing thepressure on the system to atmospheric pressure, after which a.

of 400 mm. of mercury, absolute. The product obtained contained 98.8%butadiene.

An outstanding feature of my invention is that it is preferably carriedout in a substantially non-aqueous system, or in other words in thesubstantial absence of water. Since in industrial processes of thisgeneral character the presence of some moisture is unavoidable, suchmoisture preferably should not be permitted to accumulate in quantitiesgreater than 2% by weight of solid dry salt and morepreferably notgreater than 1% by weight of said salt. Substantially lower tolerancesare recommended.

Conceivably larger-quantities of water may be present with therealization of some of the advantages of my invention but witha-sacrifice of others.

An example of fine division of the reagent salt employed in my inventionis a state of subdivision in which .the majority of the particlespresent are less than 0.05 mm. and more particularly less than 0.03 mm.in diameter.

While various procedures have been particularly described these are ofcourse subject to considerable variation. Therefore, it will beunderstood that the foregoing specific examples are given by way ofillustration, and that changes, omissions, substitutions, and/ormodifications might be made within the scope of the claims withoutdeparting from the spirit of the invention. Y

'I claim:

1; A 'process for concentrating a butadienecontaining mixture withrespect to butadiene comprising contacting said mixture with asubstantially non-aqueous reagent containing at least one solidmonovalent salt of copper to form a butadiene-reagent salt complex,removing unreacted material by distillation conducted at least in partunder subatmospheric pressure and under temperature conditions at leastas high as 25 C. but at least 5 C. below the decomposition temperatureof said butadiene-reagent salt complex under the pressure "conditionsobtaining,

and thereafter decomposing said buta'diene-re- 1 agent salt complex.

2. A process for concentrating butadiene in a light oil butadienefraction also containing hydrocarbon material having less than twodouble bonds per molecule comprising contacting said fraction with asubstantially non-aqueous reagent containing at least one solidmonovalent salt of a metal selected from the group consisting of copper,silver; and mercury to form a butadienereagent salt complex, removingunreacted material including said other hydrocarbon materialbydistillationconducted at least in part under subatmospheric pressureand under temperature conditions atleast as high as 25 C. but at least 5C. belowthe decomposition temperature of said butadiene-reagentsalt'complex under the'pressure conditions obtaining, and thereafterdecomposing said butadiene-reagent salt complex.

3. A process for obtaining butadiene in more concentrated form from a'mixture containing the same comprising contacting said mixture withsolid cuprous chloride in the absence of more than 2% by weight of waterbased on said cuprous chloride'to form a butadiene-cuprous chloridecomplex, removing unreacted material by distillation conducted at leastin part under subatmospheric pressure and under temperature conditionsat least ashigh as 25 C. but at least 5 C. below the decompositiontemperature of said butadiene-cuprous chloride complex under thepressure conditions obtaining, and thereafter decomposing saidbutadiene-cuprous chloride complex--by further heating at a temperatureat least as high as the decomposition temperature of said complex underthe pressure conditions then obtaining. I

4. A process for obtaiifing butadiene in more concentrated form from amixture containing butadiene and obtained by the pyrolysis of alcoholcomprising contacting said mixture with a reagent comprising at leastone solid monovalent salt or a metal selected from the group consistingof-copper, silver, and mercury to form a butadiene reagent saltcomplex,- said reagent con-,- taining less than 2% by weight of moisturebased on said salt, removing unreacted material by distillationconducted at least in part under subatmospheric pressure and undertemperature conthe pressure conditions then obtaining.

5. A processfor obtaining butadiene in more highly refined form from amixture containing the same and containing other hydrocarbon material of4 carbon atoms per molecule comprising contacting said mixture with areagent comprising at least one solid monovalent salt of a metalselected from the group consisting of copper,

silver, and mercury to form abutadiene-reagent salt complex, saidreagent containing less than 1% by weight of water based on said salt,removing unreacted material including said other hydrocarbon material of4 carbon atoms per molecule by distillation at least the latter part ofa which is conducted at subatmospheric pressure and under temperatureconditions at leastas high as 25 C. but at least 5 C. below thedecomposition temperature or, said butadiene-reagent salt complex at thepressure employed, and thereafter decomposing the said butadiene-reagentsalt complex by further heating at a temperature at least as high as thedecomposition temperature of said complex under the pressure conditionsthen obtaining. y I

6. A process for concentrating butadiene from a mixture containing thesame comprising contacting said mixture with a reagent comprising atleast one solid monovalent salt of a metal selected from the groupconsisting of copper, silver, and mercury to form a butadiene-reagentsalt complex, said reagent containing less than 1% by weight of moisturebased on said salt, removing unreacted material by distillation at leastthelatter part of which is, conducted at subatmos pheric pressure andunder temperature conditions at least as high as 25'' C. but at least C.below the decomposition temperature of said butadienereagent saltcomplex at the pressure employed,

and thereafter decomposing the said-butadienereagent salt complex byfurther heating under subatmospheric pressure conditions and undertemperature conditions at least as high as the decomposition temperatureof said complex under the pressure conditions'then obtaining.

'7. In a process for concentrating butadiene [contained in a mixturealso containing hydrocarbon material having less than two double bondsper molecule which comprises ,contacting said mixture with a solidmonovalent salt or a metal selected from the group consisting ofcopper,.

silver, and mercury in the absence or more than 2% by weight or waterbased on said salt, subjecting the resulting reaction mass todistillation to remove unreacted material, and decomposing saidbutadiene-reagent salt complex to recover butadiene therefrom, the stepcomprising removing unreacted material from said reaction mass bydistillation conducted under subatmospheric pressure conditions andunder temperature conditions'at least as high as C. but at least 5 C.

below the decomposition temperature of said butadiene-reagent saltcomplex under the pressure conditions obtaining.

8. In a process for recovering butadiene in more concentrated form froma mixture containing the same and also containing other hydrocarbonmaterial of'four carbon atoms per molecule and of less than two doublebonds per molecule which comprises contacting said mixture with solidcuprous chloride in the absence of more than 1% by weight of water basedon said cuprous chloride,

removing unreacted material from the reaction mass by distillationthereof, and thereafter decomposing said butadiene-reagent salt complexvby the application of heat to recover butadiene therefrom the stepscomprising removing said unreacted material from said reaction mass by40 distillation at least the latter part of which is conducted undersubatmospheric pressure conditions and under temperature conditions atleast

